1. Field of the Invention
The present invention is generally directed to a laser transmitter arrangement having at least one semiconductor laser and associated drive components.
2. Description of the Related Art
Laser transmitters having laterally coupled semiconductor lasers find important uses in communications technology because of their dynamic single-frequency operating properties. The structure and operation of such coupled semiconductor lasers are disclosed in European Patent No. 01 49 042 A2. In the disclosed arrangement, partially laterally coupled semiconductor lasers having separately drivable electrodes provide a laser transmitter having dynamic single-frequency properties that is beneficial for communications-oriented purposes. Individual lasers of the disclosed arrangement are supplied with defined operating currents which set the operating points thereof. Drive components which are required for driving the lasers are connected to the semiconductor lasers as discrete components.
A number of combinations of one or more semiconductor lasers with various drive components exist in the prior art. For example, German published application No. 3 124 633 A1 discloses a semiconductor laser having a transistor for driving the semiconductor laser which is integrated into the semiconductor layer sequence grown on a substrate. The disclosed arrangement has a characteristic feature which is that a trench having a V- shaped cross section is recessed in the upper most semiconductor layer. The trench is filled with a semiconductor material of the opposite conductivity type of the underlying material. Only various contacts for connecting electrodes are situated on the surface of the disclosed apparatus.
A published British application GB No. 2 144 912A discloses a structure having a laser diode and drive components, in which an exemplary embodiment has two transistors and an inductor. The laser diode and the drive components are mounted on a plate of ceramic that is secured within a housing. The structure in and of its self is not essential but the function of the elements interconnected in this structure is.
A published Japanese application JP No. 58-100 480 discloses a semiconductor laser format having additional semiconductor layers provided for integration of a transistor for driving the laser diode.
A published Japanese application JP No. 61-444 87 discloses an arrangement having a semiconductor laser chip, together with a circuit for protection against over-voltage, secured on a common substrate and conductively connected with a gold wire.
In a published Japanese application JP No. 61-262 77 is disclosed a semiconductor laser chip having three integrated field effect transistors. The functional elements of the disclosed structure are situated on a GaAs substrate in a vertical arrangement with the field effect transistors in the lower part and the laser diode in the upper part.
A similar structure of a semiconductor laser having an integrated field effect transistor with the field effect transistor situated in a lower part of a semiconductor layer structure and a laser diode formed in the upper semiconductor layers is disclosed by I. Ury and K. Y. Lau in Applied Physics Letters 41, pages 126 through 128 (1982).
In the publication in Applied Physics Letters 36, pages 181 through 183 (1980), T. Fukuzawa et al. disclose a semiconductor laser structure having a monolithically integrated field effect transistor, where both the laser as well as the FET are formed side by side at the surface of a semiconductor layer structure. Here, the FET also serves to drive the laser.
H. Nakano et al. in "Monolithic Integration of Laser Diodes, Photomonitors, and Laser Driving and Monitoring Circuits on a Semi-Insulating GaAs", Journal of Lightwave Technology LT-4, pages 574 through 582 (1986) recite a monolithic integration of laser diodes and photodiodes with circuits. The disclosed circuits serve to drive the laser and provide feedback for monitoring the radiant intensity of the laser. The circuits are composed of field effect transistors and of resistors which are applied to the surface of the FET. Only one laser diode and one photodiode are operated through these control circuits. A second laser diode and a second photodiode that are operated without control circuits are provided for comparison. The difference in comparison to the publications cited above is that a greater plurality of electronic function elements are monolithically integrated into the semiconductor component and the circuits have a more complex structure.